1. The Ultrastructure of Cells (1.2)
IB Diploma Biology

2. 1.2.4 Electron microscopes have a much higher resolution than light microscopes.
Resolution: making separate parts of an object distinguishable by the eye
Beams of electrons have shorter wavelengths than visible light; so much higher resolution
Resolution mm µm nm
Eye
0.1
100
100,000
Light micro.
0.0002
0.2
200
Electron micro.
0.001 1

3. Prokaryotes “Before nucleus:” evolutionary precursors to eukaryotes.
1.2.1 Prokaryotes have a simple cell structure without compartments
Prokaryotes
“Before nucleus:” evolutionary precursors to eukaryotes.
Escherichia coli (E. coli)

5. 1.2.1 Prokaryotes have a simple cell structure without compartments

6. Prokaryotic Cell Parts
cell wall: protective protein-based coating (Gram + / Gram -)
plasma membrane: selectively permeable, controls entry & exit of materials to and from the cell.
pili: attach to other bacteria for DNA transfer
cytoplasm: contains enzymes for metabolic reactions
nucleoid: closed-loop of bacterial DNA in a condensed area
ribosomes: protein synthesis (transcription & translation)
flagella: whiplash-like motion causes movement
Cell structures animation:

7. Past-paper question: E. coli TEM image
Identify these structures: I.
II.
III.
IV.
Calculate the magnification of the image.
Image from IB Biology QuestionBank CDRom – get a copy here:

8. Past-paper question: E. coli TEM image
Identify these structures:
I. Plasma membrane
II. Cell wall / pili
III. Nucleoid
IV. Cytoplasm / ribosomes
Calculate the magnification of the image. 1. Measure the scale bar in mm.
2. Multiply x 1000 to convert to μm.
That is the magnification.
How long is the bacterium?
Image from IB Biology QuestionBank CDRom – get a copy here:

11. binary fission PROKARYOTES two-parts splitting E P R O D U C through
1.2.3 Prokaryotes divide by binary fission.
PROKARYOTES E P R O D U C
through
binary fission
two-parts
splitting

12. binary fission PROKARYOTES E P R O D U C through
The closed-loop DNA of the bacterium makes copies through semi-conservative DNA replication.
New plasmids are pulled to opposing poles by fibers.
The bacterium divides in two.

14. 1.2.7 Draw the ultrastructure of prokaryotic cells based on electron micrographs.
So after absorbing all of that information, all you have to do is put it in the diagram!
Annotate: to add brief notes to a diagram or graph.

18. 1.2.2 Eukaryotes have a compartmentalized cell structure.

19. 1.2.8 Draw the ultrastructure of eukaryotic cells based on electron micrographs.

20. The Cell membrane is the boundary of the cell.
It acts as a “gatekeeper”, preventing the entry or exit of some molecules and facilitating the movement of others.
It is a phospholipid bilayer
It is permeable to oxygen and carbon dioxide
It is impermeable to water and charged particles, they must enter through special proteins embedded in the membrane
More in 2.4

21. The Nucleus contains the chromosomes which comprise most of the DNA in a cell
It is the largest organelle
It has a double layer membrane
mRNA, transcribed from DNA in nucleus, exits through pores
Some cells have multiple nuclei

22. Spot the difference? Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum

23. The ‘spots’ are the difference!
The Rough Endoplasmic Reticulum is peppered with ribosomes that give it the rough appearance
Proteins synthesized here are secreted
Smooth ER is site of lipid production

24. The internal reticular apparatus!!
I shall name it………
The internal reticular apparatus!!
Pretty catchy… no?*
Camillo
Golgi
*Everybody thought that was a terrible name, so they called it the Golgi apparatus instead

25. The Golgi Apparatus is a flattened stack of membranes responsible for the packaging and delivery of proteins

26. Lysosomes are simple, membrane-bound organelles full of enzymes that digest engulfed bacteria and viruses and large molecules for recycling.

27. The Mitochondrion (pl. Mitochondria) The ‘power house’ of the cell
Has a smooth outer membrane and a folded inner membrane
Where aerobic respiration occurs
Mitochondria in mammalian lung cells

28. Free Ribosomes: 80s sized in eukaryotes (v. 70s size in prokaryotes)
Proteins synthesized for use within the cell (i.e. enzymes used in the cytoplasm)

29. Chloroplasts Site of Photosynthesis in Plant Cells
Stacks of Thylakoids

30. Vacuoles & Vesicles:
Animal cells sometimes have small vacuoles for digestion
Unicellular organisms have contractile vacuoles for expelling water
Plant cells have large vacuoles that hold water and food
Vesicles are small lipid sacs used for transport

31. Centrioles & Microtubules:
Centrioles are bundles of microtubules found in Animal Cells
Microtubules separate chromosomes in cell division and make-up cilia and flagella

33. 1.2.8 Draw the ultrastructure of eukaryotic cells based on electron micrographs.

35. State: Give a specific name, value or other brief answer without explanation or calculation.
Plants
Have a cell wall
Have chloroplasts in photosynthetic cells
Carbohydrate stored as starch and plant oils
Rigid Shape (due to cell wall)
Have a large permanent storage vacuole
Animals
Don’t have a cell wall
Don’t have chloroplasts anywhere
Carbohydrate stored as glycogen and animal fat
Flexible shape
May have small, temporary vacuoles V.

36. Prokaryotic Eukaryotic
Compare: Give an account of similarities and differences between two (or more) items, referring to both (all) of them throughout
Prokaryotic
Eukaryotic
Small cells
Relatively larger cells
Always unicellular
Some multicellular, some unicellular
No nucleus: DNA a ‘naked’ loop in the nucleoid region
DNA in chromosomes in a membrane-bound nucleus
Ribosomes smaller (70s)
Ribosomes larger (80s)
No mitochondria, respiration in cell membrane and mesosomes
Mitochondria, where aerobic respiration occurs
Cell division by binary fission
Cell division by Meiosis or Mitosis
Reproduction asexual (some gene exchange can occur via conjugation)
Reproduction Sexual or asexual

38. 1.2.5 The structure and function of organelles within the exocrine gland cells of the pancreas.
Exocrine gland cells of the Pancreas secrete digestive enzymes into small intestine
Enzymes are proteins, so these cells must produce proteins in large quantities
Organelles involved:
Rough ER
Vesicles
Golgi Apparatus
Plasma membrane

39. 1.2.6 The structure and function of organelles within palisade mesophyll cells of the leaf.
Palisade mesophyll cells carry out most of the photosynthesis in plant cells
Organelles involved:
Chloroplasts
Mitochondria
Large Vacuole

40. 1.2.9 Interpret electron micrographs to identify organelles and deduce the function of specialized cells.

41. Identify the labeled structures in this liver cell TEM image.
Source:

42. What can you see?